Patent GB-130432-A (GB)
Title: Improvements in or relating to Electrical Signalling Systems.
IPC: H03F3/48
Filed: 1918-04-30
Abstract: 130,432. Western Electric Co., (Western Electric Co.). April 30, 1918. Wireless signalling.-An amplifying system comprising two lamp valves and their intereonnected circuits is connected to two high-frequency current sources one of which produces opposite potential variations upon the grids of the valves, while the other produces like potential variations upon the grids. One of the variable current sources is a feed-back circuit of the system or a local source of high-frequency current. When modulated high-frequency currents are supplied to the system, as in wireless telephony, the valves operate as detectors of the low-frequency variations; while, when several high-frequency currents are supplied to the system having a local source of current of a frequency equal to one of the received high-frequency currents, the outgoing circuit is provided with a filter permitting only the passage of relatively low-frequency currents. In the arrangement shown in Fig. 1, the input circuits of the thermionic valves A, B are connected in parallel with respect to the secondary winding 8 of a transformer 9, the primary winding 10 of which is connected to a source 11 of high-frequency potential variations; while the output circuits of the valves A, B are connected in parallel with respect to a battery 17 and the primary winding 18 of a transformer 19, the secondary winding 20 of which is connected to a feed-back circuit 21 containing the primary winding 16 of a transformer 15. The secondary winding 14 of the transformer 15 is connected to the grids 3, 4 of the valves. The output circuits of the valves are coupled to an outgoing circuit 26 through a transformer 22, the primary windings 23, 24 of which are wound in the same direction. The high-frequency oscillations impressed upon the transformer 9 produce no effect in the transformer 22, since the.primary windings 23, 24 are wound in the same direction. These oscillations, however, act cumulatively through the transformers 19, 15 by applying equal and opposite potential to the grids 3, 4, and the amplified oscillations are supplied to a tuned circuit 26 through the transformer 22. In the modification shown in Fig. 2, the windings 23, 24 of the transformer 22 are oppositely wound, and the circuit 11 is supplied with high-frequency oscillations modulated by low-frequency signals to which the output circuit 26 is tuned. Due to the tuning of the circuit 26, the amplified high-frequency oscillations produce no appreciable effect upon this circuit, but are fed back by the transformers 19, 15 to apply opposite potentials to the grids 3, 4 of the valve. The valve operates as a detector of the low-frequency variations which are supplied to the tuned circuit 26 through the transformer 22. In the modification shown in Fig. 3, the high-frequency, oscillations in the circuit 11 produce potential variations of opposite phase on the grids 3, 4, and, since the primary windings 30, 31 of a transformer 32 are wound in the same direction, the current fluctuations in the output circuits are additive in the secondary winding 33 in the feed-back circuit 21. The potential variations on the grids 3, 4 due to the transformer 35 are in phase, so that the re-amplified currents in the output circuits have no effect on the transformer 32, but are additive in the transformer 38, the secondary winding 39 of which is in the output circuit 26. In a further modification, the windings 30, 31 of the transformer 32, Fig. 3, are wound in opposite directions, so that the amplified high-frequency oscillations produce no effect in the feed-back circuit 21, while the rectified low-frequency variations are fed back through the circuit 21, amplified in the valves A, B, and supplied to the output circuit 26 through the transformer 38. In the arrangement shown in Fig. 5, a plurality of high-frequency oscillations in the circuit 62 are conveyed to the valves A, B through a transformer 64, and a source of high-frequency current 67 is coupled to the grid-filament circuits of the valves by a transformer 68. The frequency of the source 67 is the same as, or different from, that of one of the high-frequency oscillations in the circuit 62. The output circuits of the valves are coupled to a circuit 73 containing a filter (not shown) which permits the passage of currents below a predetermined frequency. In a modification, the input circuit is connected direct to the grids 3, 4 of the valves, the sections 65, 66 of the transformer secondary winding being replaced by two equal resistances. In the modification shown in Fig. 7, the high-frequency incoming circuit 77 is connected in the common path of the input circuits of the valves, and the local high-frequency generator is coupled to the grids 3, 4 by the transformer 78. In all the arrangements, two separate valves may be replaced by a single duplex valve. Specification 102,503 is referred to.